Interesting conundrum, how to bring in the wealth of experience that's out there while still filtering out the silliness. Thinking slightly outside the box, would not retired pilots and ATC staff be amongst the most worthy contributors? More time, experience and less axes to grind?
Then, current (verifiable) license holders, flightdeck and ATC.
All have to register and describe qualifications, confidentially and accepted on face value at first, with the proviso that your moderator(s) will be harsh with anyone suspected of posing. Free for first x months, then a questionnaire of the "is continuing on this forum worth £10/50/100 a year to you?".
Later, when the dust's settled and if you then think the contributions would be constructive, allow in others, engineers, IT etc, with the same proviso.
Easy to say all this off the cuff. We're going through something slightly similar in my own company. Have to be wary of cannibalising the existing structure. Good luck!